Thermostatic switch



Dec. 25, 1923.

H. J. SMITH wnsauosunc swrrcn Filed July 10 1920 2 Sheets-Sheet R mw EHm5 v P 0 1 A H "TO/ill s site irection, whereupon the opposite e enemaDec. 25, 1923.

UNITED STATES v 1,478,719 PATENT osncs.

men I. m 01' CHICAGO, ILLINOIS, ASSIGIOB, BY DIRECT. AID ml AIIIGI- ms,01 ODD-IOU! TO WILLARD REID AID ONE-ml '10 ALFRED EAB'IIIGB M, BOTH OISPRINGFIELD, IABSACHUBETIB.

THEBIOSTA'IIO Application filed July 10, 1990. lorlal Io. 808,424.

To all whom it may concern:

Be it known that I, HAZOR J. Surrn a citizen of the United States,residin at cisc o, in the county of Cook and tate of II mois, haveinvented certain new and useful Improvements in Thermostatic Switches,of which the following is a specification.

This invention relates to an automatic switch of the thermostat t pewhereby an electric circuitis com leted or interrupted due to a ternrature c ange.

The invention consists ntially in a bulb or container containing amedium, preferably volatile liquid, whose coeflicient of expansion ishigh or whose pressure increases rapidly with a comparatively small riseof temperature. A rise of temperature will exand the thermal mediumwhere it will flow into an expansion elementwhich will change its lengthunder the increased ressure exerted on it by the thermal me ium and thischange of length will operate a leyer to make or break an electricalcircuit. A lowerin of the temperature will cause a lessening o thepressure in the expansion element and consequently its shortening, andits shortenin is used to rotate the ever in the optpoect is had upon theelectrical circuit. Interposed between the expansion element and thelever may be placed a balanced arm for bringing about an adjustablefollow up of the action between the chan e of lengt of the expansionelement and t e lever. The best embodiment of my invention of which I amat present informed is shown by way of illustration in the attacheddrawings in which Fi re 1 shows a side elevation of the switc part ofthe invention in open position;-

F1 2 shows a detail of the switch corresponding to Fig." 1 but in closedposition;

Fig. 3 shows the wiring diagram;

Fig. 4 shows an end view of the switch with the thermostatic bulb, and

Fig. 5 shows a modification wherein a spring is substituted for a wei htfor adjusting the tension on the arm tween the expansion element and thelever.

In the drawings, the numeral 11 represents a thermostatic bulb adaptedto contain a thermal medium 12 which should be any of the volatileliquids, provided that the temperature at which the device is to bc usedis a the princi is" of operation of the switch is that the c anges in(pressure of a gas in the presence of its liqui are used to o erate theswitch. In the resent device, app cant has found sulphur ioxide (S0,)very satisfactory because of its comparatively'straight pressuretemperature line in the ra e from 20 to 40 F., it being understood t atthe dev ce is excellentl constituted for use with refrigerationmachines. If the device should be used to control a baking oven, theressure of this gas would be unduly hig so in that case, some liquidhaving a boiling point much hlgher than sulphur dioxide would have to beused.

In the tube 11 is placed any suitable stopper means 13 adapted toprevent the escape of any of the gas and tube 14 is adapted to conveythe gas rom the bulb 11 into the base 15 of the switch wherein itcommuni- .cates with the passage leading to a bellowslike expansionelement 16 provided with an upper end late 1 which end late is equippedwit a knife edge 18. Upon the base 15 of the switch there extends aforked standard 19 adapted to carry plates 20 and 21 upon which platesare supported certain elements of the switch. 22 indicates a fulcrumcarried by an upward extension 23 of the base 15.

Resting between the fulcrum 22 and the knife edge 18, is an arm 24 whichextends between the legs of the forked standard 19 and 25 indicates aweight slidably mounted upon the arm 24 having a set screw 26 forholdlng it in adjusted position upon the arm. f desired this weight mahave substituted for it a springr27 (see ig. 5) with adjusting means 28.he arm 24 has portions thereof channeled at 29 and 30 to coact with theknife edges 18 and 22 respectively. Adjacent the channel 29 the arm 24carries a trip rod 31 extending upwardly in the general ine of thecenter of the expansion element 16. The trip rod 31 carries at its upperend, an adjustable plate 32 from which depends a spring 33' and thelower end of the spring is attached to a bent extension 34 of lever orpivoted trip 35. The trip 35 is supported upon the points of two pivotscrews 36 and 3 carried by the side plates 21 and 20 respectively. Theplate 32 is made ove the boiling point of the liquid, for

adjustable to vary the tension of the s ring 33. The trip or lever 35has an insu ating arm 38 from which de ends a bridging contact bar 39preferably -shaped, having legs 40 and 41. 42 represents a stop pin forlimiting the opening movement of the lever 35. 43 and 44 representmercury cups adapted to be entered respectively by the legs 40 and 41 ofthe contact 39, and 45 and 46 respectively represent the terminals forthe mercury cups. 47 represents a fuse block and 48 a fuse. 49represents a canopy switch which may be included in the assembly forconvenience of use.

In operation, the bulb 11 is partly filled with liquid S0 and all airexhausted from the tube 14 and diaphragm bellows or other expansionelement 16 and then sealed. Now assume that the weight of the arm 24 andthe weight 25 (orthe pressure of thespring 27) is greater than thepressure upon the head 17 of the expansion element 16 exerted by the gasdue to the temperature of the bulb 11. The device will be in equilibriumand in the position shown in Figure 1. If the temperature of the bulb israised, the pressure of the S0 will be increased along the line of itspressure temperature curve and the state of equilibrium will be altered.The pressure of the gas against the head 17 of the expansion element 16will be sufficient to raise the head, the knife edge 18 and the arm 24,about its fulcrum. The raising of the lever 24'will throw the trip rod31 across the center of support of the lever on trip 35 and the tensionof the spring 33 will be exerted upon the opposite side of the center asshown in Fig. 2, whereupon the trip 35 will be pivotally moved and theconnector 39 and its legs 40 and 41 will be plunged into the mercurycups 423 and 44 and the electric circuit completed that whatever is inthe circuit, such as a motor driven compressor, will be set inoperation.

If the bulb 2 is cooled the gas pressure will be reduced, the weightedarm 24 will overcome the pressure of the as in the bellows 16 and thetrip rod 31 wil be thrown across to the opposite side of the center ofsupport of the lever the tension of the spring 33 will raise the trip 35until it strikes against the stop pin 42 and the connector 39 will bewithdrawn from the mercury cups and the circuit opened with theconsequent stoppage of the motor driven compressor or of a prime moverin the circuit.

What I claim as my invention is In a thermostatic switch of the typedescribed, the combination of a thermal element containing an expansivegas, a balanced lever actuated b a change of pressure within the thermale ement, and mounted for vertical and arcuate movement, a plate (32)adjustably carried at the upper end thereof, a spring (33) dependingfrom said plate and attached to a bent extension (34) of a pivoted trip(35), said trip carrying contacts adapted to cooperate with mercury on sto make and break an electrical circuit.

11 testimony whereof I afiix my si ature.

HAZOR J. S TH. Witnesses:

- WnmnnRmn, H, Y. Slum.

